As a result of increasingly strict environmental legislation, exhaust gas treatment systems allowing soot particles existing in combustion exhaust gases to be filtered out or eliminated are gaining in importance. In order to check or monitor the operability of such exhaust gas treatment systems, sensors are needed which allow the instantaneous particulate concentration existing in the combustion exhaust gas to be accurately determined even in extended operation. In addition, sensors of this type should allow the load of diesel particulate filters, for example, provided in an exhaust gas system to be predicted in order to achieve a high degree of system reliability, thus allowing the use of more cost-effective filter materials.
German patent document DE 102 19 798 A1 discusses a sensor for detecting substances in a fluid stream, which is designed on the basis of a ceramic multilayer substrate. It includes two measuring electrodes at a distance from each other which are exposed to the combustion exhaust gas to be studied. If soot deposits between the two measuring electrodes and a voltage is applied to the measuring electrodes, a current will flow between the measuring electrodes. Two layered heating elements make it possible to thermally free the electrodes and their surroundings from deposited soot particles. The sensor also includes a filter which is connected upstream from the measuring gas space containing the measuring electrodes, in the direction of flow of the measuring gas. The upstream filter causes coarse soot particles to deposit when the measuring gas diffuses inside the sensor. The disadvantage of this type of sensors is, on the one hand, the high cost of their manufacture and, on the other hand, the dependence of the obtained measurement results on the particle size distribution of the soot contained in the measuring gas because both the filter load from coarse particles and the measuring electrode load from fine particles influence the measurement result without the possibility of separating the two influences.
An object of the exemplary embodiment and/or exemplary method of the present invention is to provide a sensor element for sensors and a method for determining the particulate concentration in gas mixtures, which exhibits a high degree of accuracy of the obtained measuring signals while being cost-effective.